This invention relates to a thumb or finger (digital) device for attachment to a syringe, and more particularly, to a digital device comprising a tubular member attachable to the plunger of a syringe for a single-handed control of the movement of the plunger both into and out of the barrel of the syringe.
In making subcutaneous injections of certain biologicals, a grave hazard exists from the possibility that the biological can be unintentionally injected directly into a blood vessel. When a biological is injected directly into the blood stream, a generalized reaction can occur due to the extent and rapidity of the distribution of the biological material and the rapidity of the patient's reaction thereto. In order to eliminate, or at least minimize, this hazard, it is a recommended procedure that after inserting a syringe needle to make an injection, the plunger of the syringe is withdrawn a small amount to create a negative pressure within the injection chamber. If the needle point opening of the syringe has been accidentally placed within the lumen of a blood vessel, the negative pressure within the injection chamber would draw blood immediately into the syringe and, thus, provide an immediate signal to the person making the injection to terminate the procedure before the biological material contained within the injection chamber is injected. If the negative pressure yields no blood return, then it may be presumed that the needle point opening is positioned outside of any blood vessel and the biological material may be safely injected into the subcutaneous or intramuscular space where the open end of the needle point has been placed. Because it is an awkward procedure to first withdraw the plunger before injecting the biological material, the technician, nurse or physician frequently will omit this initial safety maneuver and will directly inject the biological material and run the risk of intravascular injection at the patient's hazard.
The present invention eliminates this awkwardness and provides a simple, quick and effective means not only for accomplishing withdrawal of the syringe barrel, but also the stabilization of the needle point opening in the tissues where it has been inserted. This is achieved in accordance with the invention by means of an open-ended unitary tubular member which provides a secure attachment of the head of the plunger to the thumb or finger of the person performing the injection.
Prior to the present invention, it was known to provide a thumb ring on the exposed end of a plunger of a syringe to permit the control of the movement of the plunger in both the injecting and retracting directions and such a structure would facilitate withdrawal after the needle has been inserted without the person making the injection needing to change his grip on the syringe. However, the inclusion of a thumb ring on each syringe adds to the manufacturing cost of the syringe, a factor which is particularly important with respect to disposable syringes, which are now used with increasing frequency, especially where large numbers of injections must be made, such as in hospitals. Such disposable syringes can be manufactured in sterile conditions and packaged in sterile containers prior to delivery to the point of use, and can even be prefilled with a medicinal fluid at the factory. This provision of a ring integral with the plunger on each syringe would significantly add to the cost of producing the syringes, as well as adding to the sizes of packages needed to ship and store the syringes.
Previous attempts have been made to provide detachable devices for controlling the movement of syringe plungers. Some of these prior art devices require special plunger configurations with which to mate. For example, U.S. Pat. No. 3,815,785 to Gilmont discloses a ring attached to a plunger by means of an internally threaded axial bore in the plunger. U.S. Pat. No. 1,279,069 to Yoshida requires a two-piece plunger including an inner member slideable within an outer member, in which the head of the plunger is formed on the inner member and an additional flange is formed adjacent thereto. In addition, a second additional flange is formed at the open end of the outer member, both of the additional flanges being required to maintain a detachable thumb-engageable member on the plunger.
Other prior detachable devices require the removal of the device from the thumb and a somewhat time-consuming procedure for attaching and detaching the device to the plunger of the syringe. For example, U.S. Pat. No. 2,842,128 to Hein, Jr. discloses a ring member including two arms which are threaded at one end and provided with grooves at the other end for receiving the head of the plunger. The threaded ends are received in opposite ends of a threaded sleeve and are forced toward one another upon rotation of the sleeve, whereby the grooved ends tighten around the head of the plunger. U.S. Pat. No. 2,882,901 to De Venezia discloses a ring member attached to the head of a plunger by means of a threaded retaining ring. The ring member has a cup-shaped extension having exterior threads which cooperate with interior threads formed on the retaining ring. The retaining ring has an inner diameter which is larger than the diameter of the plunger but smaller than the diameter of the head, so that the positioning of the retaining ring on the plunger requires the removal of the plunger from the barrel of the syringe. The detachment of the ring members disclosed in such prior art devices and their attachment to filled syringes constitutes an inconvenient and time-consuming procedure, especially where large numbers of injections must be administered within a very brief interval of time as in an allergist's office.